Theoretical investigation of the role of choriocapillaris blood flow in treatment of subfoveal choroidal neovascularization associated with age-related macular degeneration

Effects of donor-specific microvascular anatomy on hemodynamic perfusion in human choriocapillaris

Evidence from histopathology and clinical imaging suggest that choroidal anatomy and hemodynamic perfusion are among the earliest changes in retinal diseases such as age-related macular degeneration (AMD). However, how inner choroidal anatomy affects hemodynamic perfusion is not well understood. Therefore, we sought to understand the influences of choroidal microvascular architecture on the spatial distribution of hemodynamic parameters in choriocapillaris from human donor eyes using image-based computational hemodynamic (ICH) simulations. We subjected image-based inner choroid reconstructions from eight human donor eyes to ICH simulation using a kinetic-based volumetric lattice Boltzmann method to compute hemodynamic distributions of velocity, pressure, and endothelial shear stress. Here, we demonstrate that anatomic parameters, including arteriolar and venular arrangements and intercapillary pillar density and distribution exert profound influences on inner choroidal hemodynamic characteristics. Reductions in capillary, arteriolar, and venular density not only reduce the overall blood velocity within choriocapillaris, but also substantially increase its spatial heterogeneity. These first-ever findings improve understanding of how choroidal anatomy affects hemodynamics and may contribute to pathogenesis of retinal diseases such as AMD.

Effects of systemic drugs on the development and progression of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of severe loss of central vision among people over 50. The pathophysiology of the disease is multifactorial and can be attributed to genetics, aging, inflammation, environmental factors, and lifestyle factors including smoking, diet, obesity, and alcohol consumption. While there is no treatment for dry AMD, the current standard treatment for wet AMD is an intraocular injection of anti-vascular endothelial growth factor-an effective, yet expensive, therapy that requires ongoing treatment. As the aging population continues to grow, and AMD diagnoses continue to rise, new treatments should be explored to reduce vision complications and decrease treatment burdens. Many systemic conditions have progressive pathological changes that may affect AMD, particularly those affecting systemic vasculature like diabetes and cardiovascular status. Consequently, systemic drugs used to treat coexistent systemic diseases may influence some of the pathogenic mechanisms of AMD and lead its progression or delay. In this review we explore the current literature to summarize the findings of the reported effects of antihypertensive, immunosuppressants, cholesterol lowering agents, nonsteroidal anti-inflammatory drugs, dopamine precursors, hypoglycemic agents, and anticoagulants on AMD.

Choriocapillaris: Fundamentals and advancements

The choriocapillaris is the innermost structure of the choroid that directly nourishes the retinal pigment epithelium and photoreceptors. This article provides an overview of its hemovasculogenesis development to achieve its final architecture as a lobular vasculature, and also summarizes the current histological and molecular knowledge about choriocapillaris and its dysfunction. After describing the existing state-of-the-art tools to image the choriocapillaris, we report the findings in the choriocapillaris encountered in the most frequent retinochoroidal diseases including vascular diseases, inflammatory diseases, myopia, pachychoroid disease spectrum disorders, and glaucoma. The final section focuses on the development of imaging technology to optimize visualization of the choriocapillaris as well as current treatments of retinochoroidal disorders that specifically target the choriocapillaris. We conclude the article with pertinent unanswered questions and future directions in research for the choriocapillaris.

Anomalous Angiogenesis in Retina

Age-related macular degeneration (AMD) may cause severe loss of vision or blindness, particularly in elderly people. Exudative AMD is characterized by the angiogenesis of blood vessels growing from underneath the macula, crossing the blood–retina barrier (which comprises Bruch’s membrane (BM) and the retinal pigmentation epithelium (RPE)), leaking blood and fluid into the retina and knocking off photoreceptors. Here, we simulate a computational model of angiogenesis from the choroid blood vessels via a cellular Potts model, as well as BM, RPE cells, drusen deposits and photoreceptors. Our results indicate that improving AMD may require fixing the impaired lateral adhesion between RPE cells and with BM, as well as diminishing Vessel Endothelial Growth Factor (VEGF) and Jagged proteins that affect the Notch signaling pathway. Our numerical simulations suggest that anti-VEGF and anti-Jagged therapies could temporarily halt exudative AMD while addressing impaired cellular adhesion, which could be more effective over a longer time-span.

In vitro and computational modelling of drug delivery across the outer blood-retinal barrier

The ability to produce rapid, cost-effective and human-relevant data has the potential to accelerate the development of new drug delivery systems. Intraocular drug delivery is an area undergoing rapid expansion, due to the increase in sight-threatening diseases linked to increasing age and lifestyle factors. The outer blood-retinal barrier (OBRB) is important in this area of drug delivery, as it separates the eye from the systemic blood flow. This study reports the development of complementary in vitro and in silico models to study drug transport from silicone oil across the OBRB. Monolayer cultures of a human retinal pigmented epithelium cell line, ARPE-19, were added to chambers and exposed to a controlled flow to simulate drug clearance across the OBRB. Movement of dextran molecules and release of ibuprofen from silicone oil in this model were measured. Corresponding simulations were developed using COMSOL Multiphysics computational fluid dynamics software and validated using independent in vitro datasets. Computational simulations were able to predict dextran movement and ibuprofen release, with all of the features of the experimental release profiles being observed in the simulated data. Simulated values for peak concentrations of permeated dextran and ibuprofen released from silicone oil were within 18% of the in vitro results. This model could be used as a predictive tool for drug transport across this important tissue.

Treatment of Macular Degeneration with Sildenafil: Results of a Two-Year Trial

OBJECTIVE

To evaluate PDE5/6 inhibition with sildenafil to reduce choroidal ischemia and treat age-related macular degeneration.

METHODS

Sildenafil was prescribed to treat participants with macular degenerations or macular dystrophies measured by spectral-domain optical coherence tomography, color fundus photography, enhanced depth imaging, and best-corrected visual acuity.

RESULTS

No change in calcified drusen was noted. Vitelliform-type soft drusen were not substantially changed. A participant with Best vitelliform macular dystrophy had a significant improvement in vision as well as in photoreceptor and ellipsoid layers.

CONCLUSIONS

Our research supports sildenafil as a safe treatment for age-related and vitelliform macular degenerations. Thickened Bruch's membrane reduces the beneficial effect of perfusion increase, but all eyes appear to benefit from PDE6. Notably, maintenance or improvement in the photoreceptor layer may be the most significant result of sildenafil and is consistent with PDE6 inhibition. Thus, sil-denafil treatment of macular degeneration offers significant potential for vision retention and recovery.

Changes in Retinal and Choroidal Vascular Blood Flow after Oral Sildenafil: An Optical Coherence Tomography Angiography Study

Purpose

To describe changes in the retina and choroidal flow by optical coherence tomography angiography (OCT-A) after a single dose of oral sildenafil.

Method

A case-control study. Patients in the study group received 50 mg of oral sildenafil. Patients in the control group received a sham pill. Retinal and choroidal images were obtained at baseline (before pill ingestion) and 1 hour after ingestion. Central macular and choroidal thickness, choroidal and outer retina flow, and the retinal and choroidal vascular density were compared using a Mann-Whitney U test.

Results

Twenty eyes were enrolled into the study group and 10 eyes in the control group. There was a significant difference in central choroidal thickness and outer retina blood flow between groups after 1 hour of sildenafil ingestion (p < 0.01). There were no differences in central macular thickness, choroidal flow, and retinal vascular density among groups.

Conclusions

A single dose of oral sildenafil increases choroidal thickness, probably due to sildenafil-induced vasodilation.

Functional end-arterial circulation of the choroid assessed by using fat embolism and electric circuit simulation

The discrepancy in the choroidal circulation between anatomy and function has remained unsolved for several decades. Postmortem cast studies revealed extensive anastomotic channels, but angiographic studies indicated end-arterial circulation. We carried out experimental fat embolism in cats and electric circuit simulation. Perfusion defects were observed in two categories. In the scatter perfusion defects suggesting an embolism at the terminal arterioles, fluorescein dye filled the non-perfused lobule slowly from the adjacent perfused lobule. In the segmental perfusion defects suggesting occlusion of the posterior ciliary arteries, the hypofluorescent segment became perfused by spontaneous resolution of the embolism without subsequent smaller infarction. The angiographic findings could be simulated with an electric circuit. Although electric currents flowed to the disconnected lobule, the level was very low compared with that of the connected ones. The choroid appeared to be composed of multiple sectors with no anastomosis to other sectors, but to have its own anastomotic arterioles in each sector. Blood flows through the continuous choriocapillaris bed in an end-arterial nature functionally to follow a pressure gradient due to the drainage through the collector venule.

A Revised Hemodynamic Theory of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) afflicts one out of every 40 individuals worldwide, causing irreversible central blindness in millions. The transformation of various tissue layers within the macula in the retina has led to competing conceptual models of the molecular pathways, cell types, and tissues responsible for the onset and progression of AMD. A model that has persisted for over 6 decades is the hemodynamic, or vascular theory of AMD progression, which states that vascular dysfunction of the choroid underlies AMD pathogenesis. Here, we re-evaluate this hypothesis in light of recent advances on molecular, anatomic, and hemodynamic changes underlying choroidal dysfunction in AMD. We propose an updated, detailed model of hemodynamic dysfunction as a mechanism of AMD development and progression.

Mathematical and computational models of the retina in health, development and disease

The retina confers upon us the gift of vision, enabling us to perceive the world in a manner unparalleled by any other tissue. Experimental and clinical studies have provided great insight into the physiology and biochemistry of the retina; however, there are questions which cannot be answered using these methods alone. Mathematical and computational techniques can provide complementary insight into this inherently complex and nonlinear system. They allow us to characterise and predict the behaviour of the retina, as well as to test hypotheses which are experimentally intractable. In this review, we survey some of the key theoretical models of the retina in the healthy, developmental and diseased states. The main insights derived from each of these modelling studies are highlighted, as are model predictions which have yet to be tested, and data which need to be gathered to inform future modelling work. Possible directions for future research are also discussed. Whilst the present modelling studies have achieved great success in unravelling the workings of the retina, they have yet to achieve their full potential. For this to happen, greater involvement with the modelling community is required, and stronger collaborations forged between experimentalists, clinicians and theoreticians. It is hoped that, in addition to bringing the fruits of current modelling studies to the attention of the ophthalmological community, this review will encourage many such future collaborations.

Assessment of Choroidal Microstructure and Subfoveal Thickness Change in Eyes With Different Stages of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a major cause of irreversible blindness. Choroidal structural changes seem to be inevitable in AMD pathogenesis. Our study revealed associated choroidal microstructural changes in AMD eyes.The aim of the study was to compare choroidal microstructural changes in eyes with AMD of different stages.The study was a retrospective, cross-sectional case series.The participants comprised of 32 age-matched normal eyes as controls, and 26 fellow uninvolved eyes of intermediate/late AMD, 29 of early AMD, 28 of intermediate AMD, and 39 of late AMD.All subjects underwent comprehensive ophthalmologic examination. The choroid images, including subfoveal choroidal thickness, percentage of Sattler layer area, and en face images of the choroid, were obtained using spectral-domain optical coherence tomography.The main outcome measures were subfoveal choroidal thickness changes, percentage of Sattler layer area changes, and en face images of the choroid in AMD eyes.One hundred fifty-four eyes of 96 individuals with mean age of 67.1±9.2 years were included. The mean subfoveal choroidal thickness was 295.4 ± 56.8 μm in age-matched normal eyes, 306.7 ± 68.4 μm in fellow uninvolved eyes with AMD, 293.8 ± 80.4 μm in early AMD, 215.6 ± 80.4 μm in intermediate AMD, and 200.4 ± 66.6 μm in late AMD (F = 14.2, all P < 0.001). Choroidal thickness was greater in early AMD eyes than in intermediate/late AMD eyes (P < 0.001). Mean percentage of Sattler layer area in each group showed a similar tendency. Microstructure of the choroid showed reduced vascular density of Sattler layer areas in late AMD eyes compared with normal eyes.Decreasing subfoveal choroidal thickness and percentage of Sattler layer area were demonstrated in the progression of AMD. The choroidal change was related to atrophy of the microstructural changes of underlying capillaries and medium-sized vessels.

Ultrahigh-Speed, Swept-Source Optical Coherence Tomography Angiography in Nonexudative Age-Related Macular Degeneration with Geographic Atrophy

PURPOSE

To investigate ultrahigh-speed, swept-source optical coherence tomography (SSOCT) angiography for visualizing vascular changes in eyes with nonexudative age-related macular degeneration (AMD) with geographic atrophy (GA).

DESIGN

Observational, prospective, cross-sectional study.

PARTICIPANTS

A total of 63 eyes from 32 normal subjects and 12 eyes from 7 patients with nonexudative AMD with GA.

METHODS

A 1050-nm, 400-kHz A-scan rate SSOCT system was used to perform volumetric optical coherence tomography angiography (OCTA) of the retinal and choriocapillaris (CC) vasculatures in normal subjects and patients with nonexudative AMD with GA. Optical coherence tomography angiography using variable interscan time analysis (VISTA) was performed to assess CC alteration and differentiate varying degrees of CC flow impairment.

MAIN OUTCOME MEASURES

Qualitative comparison of retinal and CC vasculatures in normal subjects versus those in patients with a clinical diagnosis of nonexudative AMD with GA.

RESULTS

In all 12 eyes with GA, OCTA showed pronounced CC flow impairment within the region of GA. In 10 of the 12 eyes with GA, OCTA with VISTA showed milder CC flow impairment extending beyond the margin of GA. Of the 5 eyes exhibiting foveal-sparing GA, OCTA showed CC flow within the region of foveal sparing in 4 of the eyes.

CONCLUSIONS

The ability of ultrahigh-speed, swept-source OCTA to noninvasively visualize alterations in the retinal and CC vasculatures makes it a promising tool for assessing nonexudative AMD with GA. Optical coherence tomography angiography using VISTA can distinguish varying degrees of CC alteration and flow impairment and may be useful for elucidating disease pathogenesis, progression, and response to therapy.

Photodynamic Therapy and Intravitreal Bevacizumab with Versus without Triamcinolone for Neovascular Age-related Macular Degeneration; a Randomized Clinical Trial

PURPOSE

To compare the outcomes of photodynamic therapy (PDT) combined with intravitreal bevacizumab (IVB) with versus without intravitreal triamcinolone (IVT) in neovascular age-related macular degeneration (AMD).

METHODS

Eighty-four eyes with active CNV secondary to AMD with no prior treatment were enrolled and followed for 1-year. Eligible eyes were randomly assigned to either PDT/IVB or PDT/IVB/IVT. The main outcome measure was change in best-corrected visual acuity (BCVA).

RESULTS

Mean patient age was 71 ± 9 years. BCVA changes from baseline were statistically significant in both study arms at all follow-up intervals, however no significant difference was observed between the two groups regarding BCVA changes at week 12 (95% CI:-0.11-0.12 LogMAR) and other time points (all P > 0.6). Mixed model analysis revealed a significant effect from age (P < 0.001), pigment epithelial detachment (P = 0.009) and baseline BCVA (P < 0.001) on visual improvement. Significant central macular thickness (CMT) reduction occurred at all-time points as compared to baseline in both groups which was comparable between the study arms. There was no significant difference between the study arms in terms of retreatment rate (P = 0.1) and survival to the first repeat IVB injection (P = 0.065).

CONCLUSION

Additional low-dose IVT to a PDT/IVB regimen for neovascular AMD provided no beneficial effects in terms BCVA or CMT, yet demonstrated a trend toward extending the injection-free period.

Ultrahigh-speed swept-source OCT angiography in exudative AMD

BACKGROUND AND OBJECTIVE

To investigate the potential of ultrahigh-speed swept-source optical coherence tomography angiography (OCTA) to visualize retinal and choroidal vascular changes in patients with exudative age-related macular degeneration (AMD).

PATIENTS AND METHODS

Observational, prospective cross-sectional study. An ultrahigh-speed swept-source prototype was used to perform OCTA of the retinal and choriocapillaris microvasculature in 63 eyes of 32 healthy controls and 19 eyes of 15 patients with exudative AMD.

MAIN OUTCOME MEASURE

qualitative comparison of the retinal and choriocapillaris microvasculature in the two groups.

RESULTS

Choroidal neovascularization (CNV) was clearly visualized in 16 of the 19 eyes with exudative AMD, located above regions of severe choriocapillaris alteration. In 14 of these eyes, the CNV lesions were surrounded by regions of choriocapillaris alteration.

CONCLUSION

OCTA may offer noninvasive monitoring of the retinal and choriocapillaris microvasculature in patients with CNV, which may assist in diagnosis and monitoring.

Effects of photodynamic therapy with verteporfin for the treatment of chronic central serous chorioretinopathy: An uncontrolled, open-label, observational study

BACKGROUND

Central serous chorioretinopathy is an idiopathic disorder that leads to serous neurosensory retinal detachment. The disorder is usually self-limited and resolves spontaneously; however, sometimes neurosensory retinal detachment persists. This form of the disorder is called chronic central serous chorioretinopathy (CCSC).

OBJECTIVE

The aim of this study was to assess the effects of photodynamic therapy (PDT) on visual acuity with full-dose verteporfin for CCSC.

METHODS

The eyes of patients with CCSC were included in the study. Ophthalmic examination including best-corrected visual acuity (BCVA), fundus examination, fluorescein angiography, and optical coherence tomography was performed before treatment and at 1, 3, 6, 9, and 12 months. PDT with full-dose verteporfin (6 μ/m(2) of body surface area) was applied only to areas of active leakage. BCVA was converted to a log of the minimum angle of resolution (logMAR) equivalent for statistical analysis. Central foveal thickness and BCVA between baseline and follow-up were compared.

RESULTS

Seventeen eyes of 16 patients (13 males, 3 females; mean [SD] age, 39.75 [7.51] years; mean duration of follow-up, 13.06 [1.82] months) were used in the study. The mean (SEM) logMAR BCVA was 0.26 (0.07) at baseline and 0.04 (0.02) at 12 months. Mean logMAR BCVA values at baseline (0.259) and after treatment (0.112, 0.053, 0.047, 0.041, and 0.041 at 1, 3, 6, 9, and 12 months, respectively) differed significantly (P = 0.006, P = 0.005, P = 0.005, P = 0.005, and P = 0.005). There was a significant difference in the mean central foveal thickness at the final visit (169 μm) compared with the baseline value (383 μm; P < 0.001). BCVA decreased in one eye (20/20 vs 20/25) and persisted during follow-up; in the other 16 eyes, BCVA either increased (n = 10) or remained stable (n = 6).

CONCLUSIONS

In this small, open-label study, patients with CCSC treated with a single course of PDT with full-dose verteporfin had significant improvement from baseline in BCVA and resolution of subretinal fluid accumulation and active leakage. Treatment was generally well tolerated, but one patient had worsening in BCVA.

Age-related macular degeneration: choroidal ischaemia?

Aim

Our aim is to use ultrasound to non-invasively detect differences in choroidal microarchitecture possibly related to ischaemia among normal eyes and those with wet and dry age-related macular degeneration (AMD).

Design

Prospective case series of subjects with dry AMD, wet AMD and age-matched controls.

Methods

Digitised 20 MHz B-scan radiofrequency ultrasound data of the region of the macula were segmented to extract the signal from the retina and choroid. This signal was processed by a wavelet transform, and statistical modelling was applied to the wavelet coefficients to examine differences among dry, wet and non-AMD eyes. Receiver operating characteristic (ROC) analysis was used to evaluate a multivariate classifier.

Results

In the 69 eyes of 52 patients, 18 did not have AMD, 23 had dry AMD and 28 had wet AMD. Multivariate models showed statistically significant differences between groups. Multiclass ROC analysis of the best model showed an excellent volume-under-curve of 0.892±0.17. The classifier is consistent with ischaemia in dry AMD.

Conclusions

Wavelet augmented ultrasound is sensitive to the organisational elements of choroidal microarchitecture relating to scatter and fluid tissue boundaries such as seen in ischaemia and inflammation, allowing statistically significant differentiation of dry, wet and non-AMD eyes. This study further supports the association of ischaemia with dry AMD and provides a rationale for treating dry AMD with pharmacological agents to increase choroidal perfusion.

ClinicalTrials.gov registration

NCT00277784.

A randomized pilot study of low-fluence photodynamic therapy versus intravitreal ranibizumab for chronic central serous chorioretinopathy

PURPOSE

To report 6-month outcomes of a prospective, randomized study comparing the efficacy and safety between low-fluence photodynamic therapy (PDT) and intravitreal injections of ranibizumab in the treatment of chronic central serous chorioretinopathy.

DESIGN

Prospective, randomized, single-center pilot study.

METHODS

Sixteen eyes with chronic central serous chorioretinopathy were randomized to receive either low-fluence PDT or intravitreal injections of ranibizumab: 8 eyes in the low-fluence PDT group and 8 in the ranibizumab group. Rescue treatment was considered if subretinal fluid was sustained after completion of primary treatment: low-fluence PDT for the ranibizumab group and ranibizumab injection for the low-fluence PDT group. Main outcome measures were excess foveal thickness, resolution of subretinal fluid, choroidal perfusion on indocyanine green angiography, and best-corrected visual acuity.

RESULTS

At 3 months, the mean excess foveal thickness was reduced from 74.1 ± 56.0 μm to -35.4 ± 44.5 μm in the low-fluence PDT group (P = .017) and from 26.3 ± 50.6 μm to -23.1 ± 56.5 μm in the ranibizumab group (P = .058). After a single session of PDT, 6 eyes (75%) in the low-fluence PDT group achieved complete resolution of subretinal fluid and reduction of choroidal hyperpermeability, whereas 2 (25%) eyes in the ranibizumab group achieved this after consecutive ranibizumab injections. Four eyes (50%) in the ranibizumab group underwent additional low-fluence PDT and accomplished complete resolution. At 3 months, significant improvement of best-corrected visual acuity was not demonstrated in the low-fluence PDT group (P = .075), whereas it was observed in the ranibizumab group (P = .012). However, the tendency toward improvement of best-corrected visual acuity was not maintained.

CONCLUSIONS

In terms of anatomic outcomes, the effect of ranibizumab injections was not promising compared with that of low-fluence PDT.

Central serous chorioretinopathy: a pathogenetic model

Despite numerous studies describing predominantly its demography and clinical course, many aspects of central serous chorioretinopathy (CSCR) remain unclear. Perhaps the major impediment to finding an effective therapy is the difficulty of performing studies with large enough cohorts, which has meant that clinicians have focused more on therapy than on a deeper understanding of the pathogenesis of the disease. Hypotheses on the pathogenesis of CSCR have ranged from a basic alteration in the choroid to an involvement of the retinal pigment epithelium (RPE). Starting from evidence that affected subjects often present a personality prone to stress with altered pituitary–hypothalamic axis response (HPA) and that they have higher levels of serum and urinary cortisol and catecholamines than healthy subjects, we hypothesize a cascade of events that may lead to CSCR through hypercoagulability and augmented platelet aggregation. In particular we investigated the role of tissue plasminogen activator, increasing plasminogen activator inhibitor 1 (PAI-1), and plasmin-α2- plasmin inhibitor complexes. We reviewed the different therapeutic approaches, including adrenergic antagonists, carbonic anhydrase inhibitors, mifepristone, ketoconazole, laser photocoagulation, intravitreal injection of bevacizumab, and photodynamic therapy with verteporfin (PDT) and our model of pathogenesis seems to be in agreement with the clinical effects obtained from these treatments. In accord with our thesis, we began to treat a group of patients affected by CSCR with low-dose aspirin (75–100 mg), because of its effectiveness in other vascular diseases and its low ocular and general toxicity with prolonged use. The formulation of a causative model of CSCR enables us to understand how the therapeutic approach cannot be based on a generalized therapy but should be individualized for each patient, and that sometimes a combined strategy of treatment is required. Moreover a complete knowledge of the disease will help to identify patients prone to the most persistent forms of CSCR, and thus help to find a treatment.

Effect of photodynamic therapy alone or combined with posterior subtenon triamcinolone acetonide or intravitreal bevacizumab on choroidal hypofluorescence by indocyanine green angiography

PURPOSE

Choroidal hypofluorescence has been reported beneath the photodynamic therapy (PDT) site in clinical studies. We evaluated the choroidal hypofluorescence after combined PDT with posterior subtenon injection of triamcinolone acetonide or PDT with an intravitreal injection of bevacizumab for age-related macular degeneration.

METHODS

Two hundred and forty-two eyes with a subfoveal choroidal neovascularization caused by age-related macular degeneration were studied. Ninety-two eyes underwent PDT alone, 90 eyes underwent PDT with sub-Tenon injection of triamcinolone acetonide, and 60 eyes underwent PDT with intravitreal injection of bevacizumab. Verteporfin-induced choroidal hypoperfusion was determined by indocyanine green angiograms. The intensity of the diffuse fluorescence within the PDT site away from the choroidal neovascularization lesion and from the normal retina just peripheral to the optic disk was measured by densitometry (Topcon IMAGEnet computer system, Topcon, Tokyo, Japan) in the indocyanine green angiogram images obtained at 10 minutes 3 months after the PDT. The ratio of the average brightness of the retina within the PDT area to that of the retina peripheral to the optic disk (irradiated/nonirradiated retinal brightness ratio) was calculated for each angiogram.

RESULTS

The irradiated/nonirradiated retinal brightness ratio of the angiograms was 0.96 in the PDT-alone group, 0.85 in the sub-Tenon injection of triamcinolone acetonide-PDT group, and 0.89 in the intravitreal injection of bevacizumab-PDT group (Kruskal-Wallis H test, P < 0.05).

CONCLUSION

The degree of choroidal hypofluorescence in the indocyanine green angiogram images 3 months after PDT in the sub-Tenon injection of triamcinolone acetonide and intravitreal injection of bevacizumab group was higher than that of PDT-alone group. Sub-Tenon injection of triamcinolone acetonide and intravitreal injection of bevacizumab can prolong the duration of the choroidal hypofluorescence after PDT.

Temperature Distribution During ICG-Dye-Enhanced Laser Photocoagulation of Feeder Vessels in Treatment of AMD-Related Choroidal Neovascularization

Laser photocoagulation of the feeder vessels of age-related macula degeneration-related choroidal neovascularization (CNV) membranes is a compelling treatment modality, one important reason being that the treatment site is removed from the fovea in cases of sub- or juxtafoveal CNV. To enhance the energy absorption in a target feeder vessel, an indocyanine green dye bolus is injected intravenously, and the 805nm wavelength diode laser beam is applied when the dye bolus transits the feeder vessel; this tends to reduce concomitant damage to adjacent tissue. A 3D theoretical simulation, using the Pennes bioheat equation, was performed to study the temperature distribution in the choroidal feeder vessel and its vicinity during laser photocoagulation. The results indicate that temperature elevation in the target feeder vessel increases by 20% in dye-enhanced photocoagulation, compared to just photocoagulation alone. The dye bolus not only increases the laser energy absorption in the feeder vessel but also shifts the epicenter of maximum temperature away from the sensitive sensory retina and retinal pigment epithelial layers and toward the feeder vessel. Two dominant factors in temperature elevation of the feeder vessel are location of the feeder vessel and blood flow velocity through it. Feeder vessel temperature elevation becomes smaller as distance between it and the choriocapillaris layer increases. The cooling effect of blood flow through the feeder vessel can reduce the temperature elevation by up to 21% of the maximum that could be produced. Calculations were also performed to examine the effect of the size of the laser spot. To achieve the same temperature elevation in the feeder vessel when the laser spot diameter is doubled, the laser power level has to be increased by only 60%. In addition, our results have suggested that more studies are needed to measure the constants in the Arrhenius integral for assessing thermal damage in various tissues.

Effect of posterior juxtascleral triamcinolone acetonide on the efficacy and choriocapillaris hypoperfusion of photodynamic therapy

PURPOSE

To evaluate the effect of posterior juxtascleral triamcinolone acetonide (TA) injection combined with photodynamic therapy with verteporfin (PDT) for treating exudative age-related macular degeneration (AMD), the best-corrected visual acuity (BCVA), the retreatment rates and the rate of choroidal hypoperfusion were investigated.

METHODS

A total of 67 eyes with subfoveal choroidal neovascularization (CNV) due to AMD were included. Forty-four eyes underwent PDT alone (PDT-alone group), and 23 eyes underwent PDT with the posterior juxtascleral injection of TA (PDT+TA group). Every 3 months after the PDT, the eyes were evaluated with regard to BCVA and requirement for retreatment by fluorescein angiography (FA) with the aid of optical coherence tomography (OCT). Choroiocapillaris hypoperfusion was assessed by indocyanine green angiography (ICGA) at 3 and 12 months. All patients completed a 1-year follow-up.

RESULTS

At the baseline, there was no difference in lesion type, size or visual acuity between the two groups. At 1 year, the change in BCVA was -0.0811 logarithm of the minimum angle of resolution (LogMAR) in the PDT-alone group, compared with -0.0432 logMAR in the PDT+TA group. There was no significant difference in the change in BCVA between the two groups (P = 0.6910). The PDT+TA group required a lower mean number of treatments (1.64 compared with 2.34 [P = 0.0223]) and showed a higher rate of choriocapillaris occlusion at 3 months, but no significant difference at 1 year (P = 0.9243)

CONCLUSIONS

Fewer retreatments were required in the TA+PDT group. There was no significant difference in the change in BCVA between the two groups. Adjacent TA may promote short-term choriocapillaris hypoperfusion.

Transscleral drug delivery to the posterior eye: prospects of pharmacokinetic modeling

Basic biological research has provided new approaches to treat severe diseases of the retina and choroid, such as age related macular degeneration. Although it is possible to deliver drugs from a subconjunctival drug depot to the retina and choroid, the barriers and kinetics of this route of drug administration are not well known. In this review we investigate the pharmacokinetic aspects of transscleral drug delivery into the posterior eye with emphasis on pharmacokinetic modeling. The existing simulation models related to the transscleral drug delivery are reviewed and future directions for the model development are discussed. In addition, a new simulation model for the transscleral drug delivery based on permeability data is introduced. This compartmental model contains several ocular tissues (sclera, choroid, retinal pigment epithelium and vitreous) and it takes into account the clearance of the drug via choroidal circulation. The model is used to simulate the vitreous delivery of macromolecules based on the available data on FITC-dextran 70 kDa.

Different transitions of multifocal electroretinogram recordings between patients with age-related macular degeneration and polypoidal choroidal vasculopathy after photodynamic therapy

AIM

To compare and evaluate the transitions in retinal function after photodynamic therapy (PDT) between age-related macular degeneration (AMD) and polypoidal choroidal vasculopathy (PCV) using multifocal electroretinograms (mfERGs).

METHODS

10 eyes with choroidal neovascularisation (CNV) secondary to AMD and 11 eyes with CNV secondary to PCV were included in the study. mfERGs were recorded before PDT, and 1 week and 3 months after PDT. mfERG recordings were acquired by a Veris system (V.3.1.3) using a 103 hexagon stimulus. The first-order kernel was used to calculate amplitudes and latencies. Mean amplitudes and latencies from two central rings rated 0-4 degrees of visual angle were analysed and compared with each disease.

RESULTS

In AMD, the mean first negative peak (N1) amplitudes tended to decrease, and the mean first positive peak (N1P1) amplitudes reduced to significant levels (p = 0.047) 1 week after PDT. 3 months after PDT, there were no significant differences in the mean N1 and N1P1 amplitudes compared with pre-PDT values. In PCV, there were no significant changes in the mean N1 and N1P1 amplitudes 1 week after treatment. However, 3 months after PDT, mean amplitudes showed significant increases in N1 (p = 0.008) and N1P1 (p = 0.006) amplitudes compared with pre-PDT values.

CONCLUSIONS

mfERG recording transitions are different between patients with AMD and those with PCV. In patients with AMD, these results may show transient impairments in retinal function 1 week after PDT, but in those with PCV, the efficacy of PDT is superior to the impairment after PDT.

Different Plasma Levels of Vascular Endothelial Growth Factor and Nitric Oxide between Patients with Choroidal and Retinal Neovascularization

Because the blood flow is much more intense in the choroid than in the retina, it is interesting to explore whether choroidal neovascularization (CNV) is more influenced by plasma angiogenic factors than retinal neovascularization. The aim of this study was to investigate plasma profiles of vascular endothelial growth factor (VEGF) and nitric oxide (NO) in patients with CNV due to age-related macular degeneration (AMD) and in those with retinal neovascularization due to proliferative diabetic retinopathy (PDR). Seventy-seven subjects with AMD, 22 with PDR, and 42 nondiabetic, non-AMD controls were enrolled in this comparative case series. AMD subjects were classified into three groups: dry type (dry AMD, n = 17), wet type with active CNV (CNV/AMD, n = 42), and disciform scar due to advanced wet AMD (scar/AMD, n = 18). Plasma VEGF and NO levels of each subject were measured with enzyme-linked immunosorbent assay and chemiluminescence, respectively. Plasma VEGF level in CNV/AMD (median 256.0 pg/ml, interquartile range 146.4-375.3 pg/ml) was significantly higher than in PDR (124.8 pg/ml, 75.7-215.3 pg/ml; p = 0.004) and controls (120.3 pg/ml, 82.8-168.2 pg/ml, p =0.001). CNV/AMD also had the highest VEGF level among the AMD subgroups. Plasma NO level was significantly elevated in PDR (137.4 microM, 63.7-240.1 microM) when compared with CNV/AMD (71.8 microM, 42.4-113.3 microM; p = 0.004) and controls (62.6 microM, 39.0-114.9 microM; p = 0.002). There was no significant difference in NO levels among the AMD subgroups. No significant correlation between VEGF and NO levels was noted. These findings indicate that both circulating VEGF and NO may play different roles in the pathogenesis of retinal neovascularization and CNV.

Phase I clinical trial results of verteporfin enhanced feeder vessel therapy in subfoveal choroidal neovascularisation in age related macular degeneration

AIMS

To investigate the safety and effectiveness of extrafoveal photodynamic therapy (PDT) occlusion of feeder vessels (FVs) in patients with subfoveal choroidal neovascularisation (CNV) as a result of age related macular degeneration.

METHODS

FVs were identified using dynamic fluorescein and indocyanine green angiography with scanning laser ophthalmoscope. The standard doses of verteporfin and laser wavelength were used. The light dose was escalated by increasing the duration of the light dose so the light regimen was 50 J/cm2 for patients 1 and 2; 100 J/cm2 for patients 3, 4, 5; 125 J/cm2 for patients 6 and 7; and 150 J/cm2 for patients 8 and 9. Patients were examined at weeks 1, 4, and 12.

RESULTS

The mean improvement on EDTRS chart 3 months after treatment was an increase of 2.1 lines (p = 0.07). Closure of the FV was achieved angiographically in three eyes at various light doses, in three eyes the FV was hypoperfused, and in three eyes the vessels were were neither closed nor hypoperfused. At the last follow up all FVs were reperfused. There was no evidence of retinal damage.

CONCLUSION

Verteporfin enhanced FV therapy does not cause subfoveal retinal damage and may have potential to improve central vision in subfoveal CNV caused by exudative macular degeneration. It is not recommended as a monotherapy for CNV.

Feasibility of extracting velocity distribution in choriocapillaris in human eyes from ICG dye angiograms

Indocyanine green (ICG) dye angiography has been used by ophthalmologists for routine examination of the choroidal vasculature in human eyes for more than 20 years. In this study, a new approach is developed to extract information from ICG dye angiograms about blood velocity distribution in the choriocapillaris and its feeding blood vessels. ICG dye fluorescence intensity rise and decay curves are constructed for each pixel location in each image of the choriocapillaris in an ICG angiogram. It is shown that at each instant of time the magnitude of the local instantaneous dye velocity in the choriocapillaris is proportional to both the slope of the ICG dye fluorescence intensity curve and the dye concentration. This approach leads to determination of the absolute value of blood velocity in the choriocapillaris, assuming an appropriate scaling, or conversion factor can be determined. It also enables comparison of velocities in different regions of the choriocapillaris, since the conversion factor is independent of the vessel location. The computer algorithm developed in this study can be used in clinical applications for diagnostic purposes and for assessment of the efficacy of laser therapy in human eyes.

Combined photodynamic therapy and intravitreal triamcinolone injection for the treatment of subfoveal choroidal neovascularisation in age related macular degeneration: a comparative study

AIM

To evaluate the outcomes of combined intravitreal triamcinolone (IVTA) and photodynamic therapy (PDT) with verteporfin in the treatment of subfoveal choroidal neovascularisation (CNV) caused by age related macular degeneration (AMD).

METHODS

48 eyes from 48 patients with subfoveal CNV caused by AMD were prospective recruited, with 24 eyes treated with combined PDT with IVTA and compared with a control group of 24 eyes which received PDT monotherapy. In the combined treatment group, IVTA was performed immediately after PDT as an outpatient procedure. The mean number of treatments, mean logMAR best corrected visual acuity (BCVA), mean line of visual acuity changes, and proportion of patients without moderate visual loss at 1 year were compared between the combined and monotherapy groups.

RESULTS

At 1 year the logMAR BCVA for the PDT with IVTA group changed from 0.88 to 0.95 (p = 0.32 compared with baseline), whereas the logMAR BCVA for the monotherapy group reduced from 0.74 to 1.09 (p<0.001 compared with baseline). A significantly higher proportion of patients who had PDT with IVTA did not develop moderate visual loss at 1 year compared with the monotherapy group (70.8% and 33.3% respectively, p = 0.009). Eyes which had combined treatment had significantly fewer lines lost compared with monotherapy alone (0.7 and 3.5 lines respectively, p = 0.015). Subgroup analysis showed that PDT with IVTA is effective in preventing visual loss in both predominately classic and occult CNV groups. The mean number of treatments for the combined and monotherapy groups was 1.5 and 1.96 respectively (p = 0.076).

CONCLUSIONS

Combined PDT with IVTA appeared more effective statistically at 12 months for stabilisation of vision (<3 logMAR lines change) compared with PDT monotherapy. Further randomised control trials might be justified to conclude the efficacy of PDT with IVTA.

Electrooculography After Photodynamic Therapy

PURPOSE

To evaluate the changes in electrooculography (EOG) after photodynamic therapy (PDT).

METHODS

Thirty-eight eyes of 38 patients (21 males, 17 females) with choroidal neovascularization secondary to age related macular degeneration were included in this study. Standart PDT with verteporfin was performed on each patient. Serial EOG recordings were performed before, 1 week, and 1 month after PDT.

RESULTS

Mean age of the patients was 69.8+/-9.7 years (range 56 and 90 years). Seven days after PDT the visual acuity improved in 17 eyes, remained unchanged in 16 eyes and deteriorated in 5 eyes. One month after PDT the visual acuity findings were the same as the first week. New hemorrhages were seen in three eyes in the first week after PDT and visual acuity was decreased in those patients. No other patient complained of ocular and systemic adverse events. There was a statistically significant reduction in the Arden ratio of the EOG 1 week after PDT and the reduction persisted in the first month recordings.

CONCLUSIONS

The reduction in Arden ratio of EOG findings may indicate that retina pigment epithelium function could be affected after PDT.

The Changes of Pattern Electroretinography at the Early Stage of Photodynamic Therapy

PURPOSE

To evaluate the short-term changes in pattern electroretinography (PERG) after photodynamic therapy (PDT).

METHODS

Thirty eyes of 30 patients (17 males, 13 females) with choroidal neovascularization secondary to age related macular degeneration were included in this study. Standard PDT with verteporfin was performed on each patient. Serial PERG recordings were performed before, 1 week, and 1 month after PDT.

RESULTS

Mean age of the patients was 69.6+/-8.4 years (range 56 and 90 years). One month after PDT, the visual acuity improved in 16 eyes, remained unchanged in 12 eyes and deteriorated in two eyes. New hemorrhages were seen in two eyes in the first week after PDT and visual acuity was decreased in those patients. No other patient complained of ocular and systemic adverse events. There was a statistically significant reduction in the amplitudes of P50 and N95 waves at the first week recordings after PDT. At 1 month after PDT, no significant differences in the P50 and N95 amplitudes were observed compared with pre-PDT PERG recordings. There were no significant changes in the latencies of P50 and N95 at the first week and first month recordings when compared with pre-treatment PERG values.

CONCLUSIONS

Reduction in P50 and N95 amplitudes suggests that transient impairments in macular function occur at the first week after PDT.

[Transpupillary thermotherapy for occult choroidal neovascularizations]

PURPOSE

This contribution describes the results of transpupillary thermotherapy (TTT) for age-related exudative macular degeneration (AMD) with regression.

PATIENTS AND METHODS

In exudative AMD with occult choroidal neovascularization (CNV), transpupillary thermotherapy (TTT) was performed using a diode laser (Iridex) in unselected patients. Before therapy and 1, 3, and 6 months after the initial treatment the patients were examined clinically. Additionally threshold testing in the 10 degrees field (Humphrey) and fluorescein angiographies were documented at all check-ups.

RESULTS

With respect to vision, differences in the slope of the regression lines between small, medium, and large CNV were significant (p<0.001). The slope of the regressions lines was significant except for small CNV. Regarding the 10 degrees field (Humphrey), there were no statistical differences in the slope of the regression lines (p=0.867).

CONCLUSIONS

Transpupillary thermotherapy with small CNV did not show a statistically significant decrease of VA. Thus, in clinical terms early treatment of occult CNV with TTT seems to be able to prevent a further loss of visual acuity.

Photodynamic therapy and indocyanine green guided feeder vessel photocoagulation of choroidal neovascularization secondary to choroid rupture after blunt trauma

PURPOSE

To describe photodynamic therapy (PDT) and additional indocyanine green (ICG) guided feeder vessel photocoagulation as a treatment of choroidal neovascularization (CNV) secondary to choroidal rupture in case of blunt head trauma.

DESIGN

Interventional case report.

METHODS

A 61-year-old woman developed subfoveal CNV originating from a choroid tear 8 years after blunt head trauma. Four sessions of PDT were applied and an additional two consecutive sessions of selective ICG-guided feeder vessel photocoagulation conducted.

RESULTS

Transient reduction of leakage and closure of feeder vessels could not prevent further growth of the CNV.

CONCLUSIONS

PDT reduced leakage temporarily and additional ICG-guided feeder vessel photocoagulation closed treated feeder vessel and CNV. New feeder vessel formation and growth of CNV in case of traumatic choroid rupture could not be treated effectively by these two laser treatment modalities to prevent severe deterioration of visual acuity.

Roughened silver electrodes for use in metal-enhanced fluorescence

Roughened silver electrodes are widely used for surface-enhanced Raman scattering (SERS). We tested roughened silver electrodes for metal-enhanced fluorescence. Constant current between two silver electrodes in pure water resulted in the growth of fractal-like structures on the cathode. This electrode was coated with a monolayer of human serum albumin (HSA) protein that had been labeled with a fluorescent dye, indocyanine green (ICG). The fluorescence intensity of ICG-HSA on the roughened electrode increased by approximately 50-fold relative to the unroughened electrode, which was essentially non-fluorescent and increased typically two-fold as compared to the silver anode. No fractal-like structures were observed on the anode. Lifetime measurements showed that at least part of the increased intensity was due to an increased radiative decay rate of ICG. In our opinion, the use of in situ generated roughened silver electrodes will find multifarious applications in analytical chemistry, such as in fluorescence based assays, in an analogous manner to the now widespread use of SERS. To the best of our knowledge this is the first report of roughened silver electrodes for metal-enhanced fluorescence.

Transient reduction in retinal function revealed by multifocal electroretinogram after photodynamic therapy

PURPOSE

To evaluate the early changes in retinal function after photodynamic therapy (PDT) by multifocal electroretinogram (mfERG).

DESIGN

Prospective interventional case series.

METHODS

Seventeen eyes from 17 patients scheduled for standard PDT with verteporfin were prospectively recruited. Patients' diagnoses included choroidal neovascularization (CNV) secondary to age-related macular degeneration, idiopathic CNV, myopic CNV, polypoidal choroidal vasculopathy, and central serous chorioretinopathy. Serial mfERG recordings were performed before PDT, and at 4 days, 2 weeks, and 1 month after PDT. The first-order kernel N1 and P1 mfERG response from the central 0 to 7 degrees and peripheral 7 to 25 degrees were grouped and analyzed. The mean response amplitudes and peak latencies of the mfERG recordings were compared longitudinally.

RESULTS

There were statistically significant reductions in the mean N1 response amplitude for the central group at 4 days (P =.007) and 2 weeks after PDT (P =.024), in the mean P1 response amplitude for both the central (P =.006) and peripheral (P =.013) groups at 4 days, and for the central group at 2 weeks after PDT (P =.017). There were also statistically significant increases in the mean P1 response latencies at 4 days (P =.004) and at 2 weeks (P =.018) after PDT for the central group and at 4 days after PDT (P =.026) for the peripheral group. At 1 month after PDT, no significant differences in the N1 and P1 mean response amplitudes and peak latencies were observed compared with pre-PDT mfERG.

CONCLUSIONS

Transient impairments in retinal function for as long as 2 weeks after PDT were noticed by reduction in response amplitudes and a delay in peak latencies of mfERG. These findings may explain the common adverse event of subjective visual disturbance early after PDT with normal findings in visual acuity and ophthalmoscopy.

Thérapie photodynamique et DMLA : arguments pratiques sur la base de cas cliniques pour retraiter ou surveiller lors du suivi

Clinical and angiographic progression after photodynamic therapy (PDT) is usually slow, sometimes fluctuating and therefore difficult to evaluate. After several sessions of PDT, angiographic follow-up remains the basis for therapeutic management involving either a new PDT session or an alternative treatment. It remains difficult, however, to evaluate the activity and progression potential of the remaining neovessels. Imaging (angiography, optical coherence tomography) and functional data both contribute to the therapeutic decision. Certain patients require several sessions for a progressive reduction of the exudation. For others, the persistence of metamorphopsias and accentuation of the scotoma despite the treatment may entail alternative treatment. Thus, a perifoveal photocoagulation can be proposed to limit the extension of the scotoma if after a reasonable number of sessions, central visual acuity is not recovered; direct photocoagulation of a persistent active neovascular contingent, distant from the fixation zone (foveal or exenterated) can be proposed if it remains on the border of a stabilized lesion; the treatment of a feeder vessel can be proposed if it becomes visible and is associated with active neovessels with a persistent central serous detachment of the neuroretina. Lastly, performance status and patient wishes are important elements in the overall therapeutic project, especially if the eye involved is the second eye, in view of quickly initiating low-vision rehabilitation.

Clinicopathological findings of choroidal neovascularisation following verteporfin photodynamic therapy

AIMS

To report the clinicopathologic findings of surgically excised choroidal neovascularisation (CNV) three days after verteporfin photodynamic therapy (PDT).

METHODS

In three patients (three eyes) with age related macular degeneration, the CNV was surgically removed three days after PDT. The CNV specimens were examined by light microscopy.

RESULTS

The patients had subfoveal classic CNV. Fluorescein angiography revealed non-perfusion of the CNV after PDT and before surgery in all eyes. The light microscopy of the CNV membranes showed swollen and damaged endothelium. Thrombus formation or vascular occlusion in the CNV vessels was not detected.

CONCLUSION

PDT did not cause a thrombosis of the vessels within the CNV three days after PDT. Severe endothelial damage of the CNV was observed and is likely a primary effect of PDT. Non-perfusion of the CNV at this stage is possibly secondary to occlusion at a deeper level, namely the underlying feeding choroid.

Photodynamic therapy for chronic central serous chorioretinopathy

PURPOSE

To determine whether photodynamic therapy (PDT) is effective for treatment of chronic central serous chorioretinopathy (CSC).

METHODS

Sixteen eyes with chronic CSC and macular detachment documented by optical coherence tomography (OCT) received PDT guided by indocyanine green (ICG) angiography according to the parameters outlined in the TAP Study. One or more laser spots were applied to the areas of choroidal vascular hyperpermeability that corresponded to retinal pigment epithelium decompensation. Patients were observed for 6 to 12 months. Two PDT sessions 1 month apart were performed on 2 eyes. Examinations included visual acuity measurement, fundus biomicroscopy, fluorescein and ICG angiography, and OCT.

RESULTS

Macular exudation resolved completely in 13 eyes (81%) and partially regressed in 3. Choriocapillaris hypoperfusion was shown by ICG angiography for several months at the site of PDT application. Visual acuity improved 1 to 4 lines in 11 eyes and was unchanged in 5 eyes.

CONCLUSIONS

ICG-guided PDT performed according to the parameters outlined by the TAP Study seems effective for treating chronic CSC. Further studies are needed to verify treatment safety and the time and rate of recurrences.

Transpupillary thermotherapy threshold parameters: funduscopic, angiographic, and histologic findings in pigmented and nonpigmented rabbits

PURPOSE

To evaluate the effect of pigmentation on threshold fluence levels, needed to produce visible and angiographic lesions, of transpupillary thermotherapy (TTT) in rabbits.

METHODS

Six pigmented and nine nonpigmented rabbits underwent TTT with an 810-nm diode laser coupled to a slit-lamp biomicroscope using a spot size of 2 or 3 mm. The power ranged from 80 to 200 mW with 1 to 3 minutes of laser exposure for pigmented rabbits and 750 to 1800 mW with 1 minute of exposure for albino rabbits. These parameters were also evaluated after compression of the globe using the contact lens to induce blanching of the optic nerve head. After the experiment, the eyes were enucleated under deep anesthesia, and the animals were killed immediately.

RESULTS

In pigmented rabbits, the threshold fluence with the 2-mm spot size was 229 J/cm2 without compression and 153 J/cm2 with compression. With the 3-mm spot size, the threshold decreased from 200 to 150 mW as the duration of exposure lengthened (2 or 3 minutes), increasing the fluence from 170 to 382 J/cm2. In nonpigmented rabbits, the threshold fluence with the 2-mm spot size was 2,865 J/cm2 without compression and 2,674 J/cm2 with compression. With the 3-mm spot size, the threshold fluence of 1,528 J/cm2 was not affected by compression. Histopathologic studies showed transretinal damage at the lowest levels necessary to achieve angiographic evidence of a treatment lesion or a barely visible funduscopic lesion at the time of treatment.

CONCLUSIONS

Nonpigmented rabbits required more than a 12-fold increase in total TTT fluence compared with pigmented rabbits with the 2-mm spot size and a ninefold increase with the 3-mm spot size. Inner and outer retinal damage was seen histopathologically at these levels.

Transpupillary thermotherapy threshold parameters: effect of indocyanine green pretreatment

PURPOSE

To evaluate the effect of combined treatment with systemic indocyanine green (ICG) on threshold fluence levels of transpupillary thermotherapy (TTT) in rabbits.

METHODS

Four pigmented rabbits and 13 nonpigmented rabbits were studied. TTT was performed on normal rabbit choriocapillaris using an 810-nm diode laser via slit-lamp biomicroscope delivery through a Goldmann macular lens. Laser spot size, power, and duration of laser exposure were varied to achieve a range of TTT fluences for threshold testing in both albino and pigmented rabbit fundi. Intravenous ICG pretreatment at doses of 0.41 to 10 mg/kg was initiated at varying times before TTT treatment. After the experiment, the eyes were enucleated under deep anesthesia, the animals were killed, and the eyes were prepared for light microscopy.

RESULTS

When intravenous ICG pretreatment was employed, there was a dose-dependent decrease in the TTT fluence threshold as compared with known threshold values. At threshold fluences, histopathologic sections revealed damage to all layers of the retina in addition to choriocapillaris damage.

CONCLUSION

Intravenous ICG pretreatment can be used to lower the TTT threshold fluence and irradiance required to create angiographically visible lesions in the normal rabbit choriocapillaris. Damage was seen in all layers of the retina and choriocapillaris at threshold levels when TTT was used alone or in combination with ICG pretreatment.

Metal-Enhanced Fluorescence (MEF) Due to Silver Colloids on a Planar Surface: Potential Applications of Indocyanine Green to in Vivo Imaging

We examined the effects of metallic silver colloids on the fluorescence spectral properties of indocyanine green (ICG), which is a dye widely used for in vivo medical testing. Silver colloids from a suspension bind spontaneously to amine-coated surfaces. These colloid-coated surfaces were found to cause a 30-fold increase in the intensity of ICG, which was held close to the metal surface by adsorbed albumin. The increased intensities of ICG were also associated with decreased lifetimes and increased photostability, which are indicative of modifying the fluorophores radiative decay rate. These results suggest the use of metal colloid-enhanced ICG for applications to retinal angiography and vascular imaging and as a contrast agent for optical tomography.

Clinicopathologic study after submacular removal of choroidal neovascular membranes treated with verteporfin ocular photodynamic therapy

PURPOSE

To report the clinicopathologic findings after submacular removal of choroidal neovascular membranes (CNV) treated with verteporfin ocular photodynamic therapy.

DESIGN

Interventional case series.

METHODS

Retrospective review of eight eyes of eight patients who underwent submacular surgery for CNV after having previously received verteporfin ocular photodynamic therapy for presumed ocular histoplasmosis (one patient), age-related macular degeneration ([AMD] three patients) pathologic myopia (two patients), punctate inner choroiditis (one patient), and idiopathic CNV (one patient). All cases had undergone ocular photodynamic therapy with verteporfin using standard protocols. Six of eight patients suffered a submacular hemorrhage after ocular photodynamic therapy, and two of eight patients refused further ocular photodynamic therapy. All patients subsequently had submacular surgery with removal of the CNV. One membrane was routinely processed, sectioned, and stained with hematoxylin and eosin. Five membranes were stained with toluidine blue for light microscopic examination. Semithin (1.0 microm) sections were cut and stained with uranyl acetate-lead citrate for transmission electron microscopy.

RESULTS

Choroidal neovascular membranes were removed at 3 days (presumed ocular histoplasmosis), 29 days (punctate inner choroiditis), 63 days (AMD, pathologic myopia), 66 days (AMD), 107 days (pathologic myopia), 116 days (AMD), and 152 days (idiopathic) after verteporfin ocular photodynamic therapy. Histopathologic and ultrastructural examination showed areas of vascular occlusion at 3 days that were not seen at later time points. All specimens had patent CNV. There were signs of vascular damage with extravasated erythrocytes and fibrin, pigment clumping in cells, and inflammatory cells in all but the 3-day specimen.

CONCLUSIONS

This case series presents data only from patients who refused repeat treatment with ocular photodynamic therapy or who developed submacular hemorrhage after initial photodynamic therapy. Histopathologic evaluation of CNV 3 days after verteporfin ocular photodynamic therapy showed partial vascular occlusion that was not present in later specimens. These later specimens demonstrated evidence of vascular damage. Verteporfin ocular photodynamic therapy does not appear to lead to permanent and complete occlusion of the CNV. Thus, treatments that lead to permanent closure of CNV without damage to the retinal pigment epithelium and sensory retina are still needed.